Mobile communications networks typically utilize a plurality of base stations to connect mobile communication subscriber stations to a wireless network. Each of the mobile communication subscriber stations initially communicates with a base station to exchange information with the wireless network when located in a cell area serviced by the base station. However, the calls being supported for such mobile communication subscriber stations often must be handed off to different base stations when the mobile communication subscriber stations physically move from cell to cell or when the current servicing base station experiences congestion while servicing other mobile communication subscriber stations.
Institute of Electrical and Electronics Engineers (“IEEE”) 802.16e and other future wireless systems will have support for both frequency selective (a.k.a. band adaptive modulation and coding (“AMC”) mode) and frequency diverse operations, potentially within the same data frame by dividing (in time) a frame into a frequency selective and a frequency diverse zone. It is not, however, known how to assign a user terminal for a frequency diverse or a frequency selective zone for the best system performance.
Current wireless systems assign frequency selective or frequency diverse allocations based on, for example, the speed of the user terminal moving through the cell. The user terminal being serviced could include a Doppler detector to detect the speed of the user terminal. The base station may also make a determination of the location of the user terminal as a function of time. In both instances, however, the precise location of the user terminal is not ascertained.
In some current systems, frequency selective allocations are given to user terminals having “trustworthy” channel-quality information (“CQI”) calculations. These CQI calculations take into account instantaneous fading and interference characteristics experienced by the user terminal. However, basing the assignment of the frequency selective allocation based on CQI can result in user terminals being assigned frequency selective allocations even though they are located near a cell boundary and are likely to experience uneven intercell interference.
By utilizing only CQI calculations and/or the speed of the user terminal's movement to make the assignment of frequency selective or frequency diverse allocations, incorrect allocations are often made, resulting in reduced system performance and excessive bandwidth usage.
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